Tag: astronomy

Asteroid that formed in the inner solar system discovered in Kuiper Belt

9:24 am

Astronomers have discovered a carbonaceous asteroid in the distant Kuiper Belt beyond Pluto, even though it likely formed in the inner solar system.

The asteroid’s existence serves to confirm models of the solar system’s formation that say that the orbits of gas giants migrate inward and outward during the formation process, and as they do so they can fling material out of the inner solar system. This asteroid is the first evidence of this process.

At the same time, the data here is quite slim. They have only found one such asteroid. It could be that it was flung into the Kuiper Belt by other processes. If the formation model is correct, many more such Kuiper Belt asteroids will be eventually be found.

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Astronomers find evidence for thousands of black holes near galaxy center

8:46 am

The uncertainty of science: Using data from the Chandra X-Ray Observatory, astronomers have found evidence suggesting that thousands of stellar-mass black holes might exist circling Sagittarius A* (pronounced A-star), the super-massive black hole at the center of the Milky Way.

Essentially, they found a dozen likely black hole candidates in what they think are X-ray binaries system. From this they extrapolate the number of potential stellar-massed black holes at the center of the galaxy. However,

While the authors strongly favor the black hole explanation, they cannot rule out the possibility that up to about half of the observed dozen sources are from a population of millisecond pulsars, i.e., very rapidly rotating neutron stars with strong magnetic fields.

In other words, this conclusion is very uncertain. Nonetheless, even if half of their candidates are not stellar-mass black holes, the results do suggest that there are a very large number of black holes circling Sagittarius A*. Using this information astronomers will be able to better refine their theories on the formation process for such super-massive black holes.

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Pluto is a planet

9:51 am

In an op-ed today, the principal investigator for the New Horizons’ mission as well as his co-author for the history of that mission explained in detail why the definition for planet as imposed by the International Astronomical Union (IAU) is flawed and unworkable.

In 2006, the International Astronomical Union (IAU) announced an attempted redefinition of the word “planet” that excluded many objects, including Pluto. We think that decision was flawed, and that a logical and useful definition of planet will include many more worlds.

We find ourselves using the word planet to describe the largest “moons” in the solar system. Moon refers to the fact that they orbit around other worlds which themselves orbit our star, but when we discuss a world like Saturn’s Titan, which is larger than the planet Mercury, and has mountains, dunes and canyons, rivers, lakes and clouds, you will find us — in the literature and at our conferences — calling it a planet. This usage is not a mistake or a throwback. It is increasingly common in our profession and it is accurate.

Most essentially, planetary worlds (including planetary moons) are those large enough to have pulled themselves into a ball by the strength of their own gravity. Below a certain size, the strength of ice and rock is enough to resist rounding by gravity, and so the smallest worlds are lumpy. This is how, even before New Horizons arrives, we know that Ultima Thule is not a planet. Among the few facts we’ve been able to ascertain about this body is that it is tiny (just 17 miles across) and distinctly nonspherical. This gives us a natural, physical criterion to separate planets from all the small bodies orbiting in space — boulders, icy comets or rocky and metallic asteroids, all of which are small and lumpy because their gravity is too weak for self-rounding.

They go on to explain the flawed history of the IAU definition, and how it has simply not been accepted by astronomers and planetary scientists alike. The definition makes no sense, and excludes the thousands of exoplanets discovered orbiting other stars. They also point to a proposed new definition that is simple and admits to reality.

A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.

Whether or not the stuffed shirts at IAU ever officially endorse this definition, it is the one that human beings are using now, and it will be the one they use into the never-ending future.

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The aging data relay spacecraft orbiting Mars

9:40 am

By the 2020s, NASA and other space agencies sending landers and rovers to Mars will be faced with a data-relay crisis, as the orbiters they presently use to provide communications with the Martian surface are aging, and no replacements are presently planned.

The venerable Mars Global Surveyor (MGS) and Mars Odyssey spacecraft were the first to employ data relay capabilities in the modern era of Mars exploration. They operated as relays for the twin Mars Exploration Rover missions until the arrival of the Mars Reconnaissance Orbiter (MRO) in 2006.

MGS entered into a safe mode in November 2006 and NASA later declared the mission over in January 2007 after the space agency failed to reestablish contact with the aging orbiter. The 12-year-old MRO and 17-year-old Odyssey have served as the primary data relays for Mars surface missions since.

More important, funding for a dedicated communications satellite called NEMO, planned for launch in 2022, has disappeared.

However, funding for NeMO has been largely phased out in favor of directing limited funds towards the development of the Mars Sample Return mission. Mars Sample Return has the primary objective of fetching samples that scientists plan to collect and cache using the Mars 2020 rover currently under development. The current Planetary Science Decadal Survey has listed the flagship sample return mission as the primary objective for NASA’s Mars program in the 2020s, along with requisite funding. The existing fleet of orbiting spacecraft at Mars, while aging, are in generally good health meaning the postponement of a new orbiter will require careful management of existing orbital assets into the next decade.

One of the reasons there is no funding for NEMO is that NASA has had to steal money from its planetary program to fund the cost overruns on the James Webb Telescope. Though this was never admitted publicly, the cuts that the Obama administration imposed on the planetary program were partly to pay for Webb. Thus, not only has that telescope killed almost all of NASA’s entire astrophysics program, it has damaged the planetary program as well.

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Hubble detects helium in exoplanet atmosphere

2:57 pm

Using the Hubble Space Telescope astronomers have for the first time detected helium in the atmosphere of an exoplanet.

The team made the detection by analysing the infrared spectrum of the atmosphere of WASP-107b [1]. Previous detections of extended exoplanet atmospheres have been made by studying the spectrum at ultraviolet and optical wavelengths; this detection therefore demonstrates that exoplanet atmospheres can also be studied at longer wavelengths.

…WASP-107b is one of the lowest density planets known: While the planet is about the same size as Jupiter, it has only 12% of Jupiter’s mass. The exoplanet is about 200 light-years from Earth and takes less than six days to orbit its host star.

The amount of helium detected in the atmosphere of WASP-107b is so large that its upper atmosphere must extend tens of thousands of kilometres out into space. This also makes it the first time that an extended atmosphere has been discovered at infrared wavelengths. Since its atmosphere is so extended, the planet is losing a significant amount of its atmospheric gases into space — between ~0.1-4% of its atmosphere’s total mass every billion years

The important aspect of this detection is the use of infrared, which gives astronomers another tool to study exoplanets.

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Gaia releases 3D map of galaxy

8:17 am

The science team for the space telescope Gaia, designed to map the positions of billions of stars, have released the probe’s second catalog, producing a 3D map of 1.7 billion stars in the Milky Way

The new data release, which covers the period between 25 July 2014 and 23 May 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision. For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a Euro coin lying on the surface of the Moon.

With these accurate measurements it is possible to separate the parallax of stars – an apparent shift on the sky caused by Earth’s yearly orbit around the Sun – from their true movements through the Galaxy. The new catalogue lists the parallax and velocity across the sky, or proper motion, for more than 1.3 billion stars. From the most accurate parallax measurements, about ten per cent of the total, astronomers can directly estimate distances to individual stars.

The catalog provides much more information than this. For example:

As well as positions, the data include brightness information of all surveyed stars and colour measurements of nearly all, plus information on how the brightness and colour of half a million variable stars change over time. It also contains the velocities along the line of sight of a subset of seven million stars, the surface temperatures of about a hundred million and the effect of interstellar dust on 87 million.

Gaia also observes objects in our Solar System: the second data release comprises the positions of more than 14 000 known asteroids, which allows precise determination of their orbits. A much larger asteroid sample will be compiled in Gaia’s future releases.

Further afield, Gaia closed in on the positions of half a million distant quasars, bright galaxies powered by the activity of the supermassive black holes at their cores. These sources are used to define a reference frame for the celestial coordinates of all objects in the Gaia catalogue, something that is routinely done in radio waves but now for the first time is also available at optical wavelengths.

I guarantee that many theories about specific strange stars, such as the plethora of different types of variable stars, are going to change drastically with this new and precise information. At the article they describe just one example relating to white dwarf stars.

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How to blow up a star

8:29 am

Link here. The story details the new supercomputer simulation work attempting to model the internal processes inside a dying star that cause it to explode as a supernova.

For more than half a century, physicists have suspected that the heat produced by elusive particles called neutrinos, created in the core of a star, could generate a blast that radiates more energy in a single second than the Sun will in its lifetime. But they have had trouble proving that hypothesis. The detonation process is so complex — incorporating general relativity, fluid dynamics, nuclear and other physics — that computers have struggled to mimic the mechanism in silico. And that poses a problem. “If you can’t reproduce it,” Janka says, “that means you don’t understand it.”

Now, improvements in raw computing power, along with efforts to capture the stellar physics in acute detail, have enabled substantial progress. Janka’s simulation marked the first time that physicists had been able to get a realistic 3D model of the most common type of supernova to explode. Just months later, a competing group based at Oak Ridge National Laboratory in Tennessee repeated the feat with a heavier, more complex star. The field is now buzzing, with more than half a dozen teams currently working on exploding stars in 3D.

They have apparently solved one problem, figuring out how the neutrino blast wave gets enough energy to blast free from the star’s core. A close read of the article indicates that, while progress has been made, they still have many gaps of their understanding.

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Diamonds from space!

9:46 am

Researchers have discovered nano-sized diamonds inside a recovered meteorite that suggest a formation process deep within a planet at least the size of Mercury.

The researchers used transmission electron microscopes to determine their composition and morphology, and found that the diamonds contained inclusions (impurities) made of chromite, phosphate and iron-nickel sulfides.

These inclusions are common in diamonds formed underground here on Earth, but this marks the first time they’ve been found in alien rocks. That’s interesting enough on its own, but it has much bigger implications – the team calculated that these diamonds could only have formed under pressure of more than 20 gigapascals. That means they must have been born inside a planet at least as big as Mercury, and possibly up to the size of Mars.

But there’s still more to the story. The fact these diamonds made it to Earth implies that their home planet, whatever it may have been, is no longer with us, since it would take quite a cataclysm to wrench them out of their birthplace deep underground and fling them into space. Instead, the team believes the diamonds came from a planetary embryo.

Not so fast. Though the researchers themselves, in the released paper, assume that the diamonds could only have formed from inside a now destroyed large planet, this leaves out the possibility that the diamonds formed inside one of the existing terrestrial planets, were moved upward toward the surface by later geological process (as happens to diamonds are here on Earth), and then were thrown from the planet by a later nearby impact. This scenario is just as likely.

Nonetheless, this discovery is fascinating. More than anything, it illustrates the inconceivable amount of time that has passed in creating our solar system. Any of these scenarios requires time, time in quantities that no human can really understand or conceptualize.

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More delays threaten the Thirty Meter Telescope in Hawaii

9:48 pm

The coming dark age: The delaying tactics of the opponents to building the Thirty Meter Telescope in Hawaii has caused the consortium to announce that it now seriously considering moving the telescope to Spain’s Canary Islands.

These have been the most recent delaying tactics:

On Thursday, the Hawaii Senate approved a bill to ban new construction atop Mauna Kea, and included a series of audits and other requirements before the ban could be lifted. But House leaders said they don’t have plans to advance the bill. Democratic House Speaker Scott Saiki told the Honolulu Star-Advertiser that the “bill is dead on arrival in the House.”

There are also two appeals before the Hawaii Supreme Court. One challenges the sublease and land use permit issued by the Hawaii Board of Land and Natural Resources. The other has been brought by a Native Hawaiian man who says use of the land interferes with his right to exercise cultural practices and is thus entitled to a case hearing.

When the telescope gets moved, expect these barbarians in Hawaii to celebrate loudly, claiming their victory as a victory for “native rights.” What they will really be telling us is two things. First, they are against gaining new knowledge and new technology in a manner that does no one any harm. And two, they put racial rights above all, making them the worst sort of bigots.

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The search for exoplanets at Alpha Centauri

8:56 am

The search for new exoplanets orbiting the three stars of the Alpha Centauri star system is intensifying, despite significant viewing challenges and solar activity that precludes life around one star.

The system’s two sunlike stars, Alpha Centauri A and B, orbit each other closely while Proxima Centauri, a tempestuous red dwarf, hangs onto the system tenuously in a much more distant orbit. In 2016, astronomers discovered an Earth-mass planet around Proxima Centauri, but the planet, blasted by radiation and fierce stellar winds, seems unlikely to be habitable. Astrobiologists think the other two stars are more likely to host temperate, Earth-like planets.

Maksym Lisogorskyi, an astronomer at the University of Hertfordshire in Hatfield, U.K., tried to find them with an instrument on the European Southern Observatory’s (ESO’s) 3.6-meter telescope in Chile. He and his colleagues looked for Doppler shifts in the spectral lines of the stars’ light that would be caused if a planet tugged them back and forth. But Lisogorskyi told the meeting that the stars’ surfaces are turbulent, and prone to flares that also jiggle the spectral lines, masking the subtle signals from any Earth-size planets. “The lines do all kinds of things,” he says. Although Alpha Centauri has been a primary target for the planet-finding instrument since it was inaugurated in 2005, it has seen nothing so far.

Also hampering observations are the current positions of the two stars. As viewed from Earth, they are very close together, making them harder to study individually, Lily Zhao of Yale University told the meeting. More precise observations should become possible as their 80-year orbit carries them farther apart. In the meantime, Zhao and her colleagues have succeeded in ruling out the presence of giant planets around either star, based on a decade’s worth of data from three instruments on different telescopes. “There are no Jupiters in the system, but there may be plenty of Earth-sized planets still to discover,” she said.

I am skeptical of the conclusions of the astrobiologists who think there may be habitable Earth-like planets in orbit around the close binary. Binary formation makes planetary formation difficult, and even if they are there the stars’ orbits would make stable orbits unlikely. Nonetheless, the research is good, as the techniques learned will be applicable elsewhere.

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Astronomers find a dozen black holes near center of Milky Way

8:40 am

Astronomers have discovered a dozen smaller black holes orbiting near Sagittarius A* (pronounced “A-star”), the supermassive black hole at the center of the Milky Way.

Charles Hailey from Columbia University in New York and colleagues used archival data from Nasa’s Chandra X-ray telescope to come to their conclusions. They report the discovery of a dozen inactive and low-mass “binary systems”, in which a star orbits an unseen companion – the black hole.

The supermassive black hole at the centre of the Milky Way, known as Sagittarius A* (Sgr A*), is surrounded by a halo of gas and dust that provides the perfect breeding ground for the birth of massive stars. These stars live, die and could turn into black holes there. In addition, black holes from outside the halo are believed to fall under the influence of Sgr A* as they lose their energy, causing them to be pulled into its vicinity, where they are held captive by its force. Some of these bind – or “mate” – to passing stars, forming binary systems.

They have extrapolated their data to predict the existence of thousands more of these small black holes near the galaxy’s center.

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Hubble finds galaxy with no evidence of dark matter

12:29 pm

The uncertainty of science: Using the Hubble Space Telescope astronomers have discovered a nearby galaxy that apparently has little or no evidence of dark matter.

The unique galaxy, called NGC 1052-DF2, contains at most 1/400th the amount of dark matter that astronomers had expected. The galaxy is as large as our Milky Way, but it had escaped attention because it contains only 1/200th the number of stars. Given the object’s large size and faint appearance, astronomers classify NGC 1052-DF2 as an ultra-diffuse galaxy. A 2015 survey of the Coma galaxy cluster showed these large, faint objects to be surprisingly common.

But none of the ultra-diffuse galaxies discovered so far have been found to be lacking in dark matter. So even among this unusual class of galaxy, NGC 1052-DF2 is an oddball.

Van Dokkum and his team spotted the galaxy with the Dragonfly Telephoto Array, a custom-built telescope in New Mexico they designed to find these ghostly galaxies. They then used the W.M. Keck Observatory in Hawaii to measure the motions of 10 giant groupings of stars called globular clusters in the galaxy. Keck revealed that the globular clusters were moving at relatively low speeds, less than 23,000 miles per hour. Stars and clusters in the outskirts of galaxies containing dark matter move at least three times faster. From those measurements, the team calculated the galaxy’s mass. “If there is any dark matter at all, it’s very little,” van Dokkum explained. “The stars in the galaxy can account for all the mass, and there doesn’t seem to be any room for dark matter.”

The galaxy is unusual in many other ways.

The Hubble images also revealed the galaxy’s unusual appearance. “I spent an hour just staring at the Hubble image,” van Dokkum recalled. “It’s so rare, particularly these days after so many years of Hubble, that you get an image of something and you say, ‘I’ve never seen that before.’ This thing is astonishing: a gigantic blob that you can look through. It’s so sparse that you see all of the galaxies behind it. It is literally a see-through galaxy.”

The ghostly galaxy doesn’t have a noticeable central region, or even spiral arms and a disk, typical features of a spiral galaxy. But it doesn’t look like an elliptical galaxy, either. The galaxy also shows no evidence that it houses a central black hole. Based on the colors of its globular clusters, the galaxy is about 10 billion years old. Even the globular clusters are oddballs: they are twice as large as typical stellar groupings seen in other galaxies.

The bottom line here is that we have only circumstantial evidence that dark matter exists, based solely on the fact that in all other measured galaxies, the outer stars rotate much faster than they should. That rotation speed however does not guarantee the existence of dark matter, only that something is causing the fast rotation. And the lack thereof in this galaxy puts a big crimp in the theory that dark matter exists, since the theories that posit its existence almost require it to be present in every galaxy.

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